Prepends a new row to tree_store. If parent is non-null, then it will prepend
the new row before the first child of parent, otherwise it will prepend a row
to the top level. iter will be changed to point to this new row. The row
will be empty after this function is called. To fill in values, you need to
call gtk.tree_store.TreeStore.set or gtk.tree_store.TreeStore.setValue.
Prepends a new row to tree_store. If parent is non-null, then it will prepend the new row before the first child of parent, otherwise it will prepend a row to the top level. iter will be changed to point to this new row. The row will be empty after this function is called. To fill in values, you need to call gtk.tree_store.TreeStore.set or gtk.tree_store.TreeStore.setValue.